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yap-6.3/Logtalk/examples/symdiff/log1.lgt

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:- object(log(_),
implements(symdiffp)).
:- info([
authors is 'Paulo Moura',
version is 1.0,
date is 1999/12/29,
parnames is ['Expression'],
comment is 'Symbolic differentiation and simplification of log/1 expressions.',
source is 'Example based on the Clocksin and Mellish Prolog book.']).
diff(Diff) :-
this(log(X)),
once(diff(X, Diff)).
diff(I, 0) :-
integer(I).
diff(X, DX * X ** -1) :-
X::diff(DX).
simplify(S) :-
this(log(X)),
once(simplify(X, S)).
simplify(1, 0).
simplify(I, Log) :-
integer(I),
Log is log(I).
simplify(X, X).
:- end_object.